1. Technical Field
This invention relates to a resonator and a filter including the same.
2. Description of the Related Art
With advancement in wireless communication technology, various wireless communication systems using a frequency band of microwaves or millimeter waves as carrier waves have been developed. Also, data can be easily transmitted or received in various indoor/outdoor places using the various wireless communication systems.
Various radio-frequency (RF) filters are applied to communication devices used in a communication system. The RF filters are devices that pass only signals of a predetermined frequency band, and are classified into a low-pass filter (LPF), a band-pass filter (BPF), a high-pass filter (HPF), a band stop filter (BSF), etc. according to a frequency band to be filtered.
Recently, as mobile communications have been developed, high-frequency bands have been frequently used and resonators capable of achieving both narrow-band characteristics and high blocking characteristics are required. The existing resonators are disadvantageous in that a stop-band is very narrow and an undesired pass band periodically occurs.